When will I ovulate after my period starts?

You know the day your period started. Now you want to know when you’ll ovulate. On a 28-day cycle it’s usually about 14 days after the first day of your period. Your own cycle length moves that date, and the tables below do the counting for you.

How many days after your period do you ovulate?

Ovulation is tied to your next period, not your last one. The NHS says it happens around 10 to 16 days before the next period in most women. The days after ovulation stay fairly steady from cycle to cycle. The days before it are the part that stretches or shrinks. So a longer cycle means you ovulate later, and a shorter one means sooner.

Always count from the first day of your period. The NHS calls that day 1 of your cycle. Find your usual cycle length below and read across. Every number is days after your period started. “Ovulation” is the best guess, 14 days before your next period. “Could be” is the full range the NHS gives.

The fertile days are ovulation day plus the five days before it, because sperm can live that long and an egg lasts about a day. The fertile window guide explains where those numbers come from. If you don’t know your cycle length, put your last few start dates into the cycle length calculator.

My period started on the 17th. When will I ovulate?

Here’s every start date in a month on a 28-day cycle. Find the day your period started and read across. The table counts in a 31-day month like January. If your month is shorter, any date that rolls into next month comes a day later for a 30-day month and three days later after February.

If your cycle isn’t 28 days, shift every date by the difference. A 31-day cycle is three days longer, so ovulation comes about three days later than the table says. A 25-day cycle puts it about three days sooner. The free period calculator does this with real dates, for your cycle length, six cycles ahead.

Does the length of your period change when you ovulate?

No. A 3-day period and a 7-day period on the same 28-day cycle put ovulation on the same day. What moves ovulation is how long the whole cycle runs, from the first day of one period to the first day of the next. So count from the day the bleeding started, not the day it stopped. Counting from the last day puts the estimate several days late.

Why the date is only an estimate

The NHS says it’s difficult to pinpoint exactly when ovulation happens. It also says a woman with a regular 28-day cycle is likely to be fertile around day 14, and that this won’t apply to shorter or longer cycles. Your own ovulation can move a few days from one month to the next. Stress, illness and travel can push it later. If your cycles vary a lot, the irregular period calculator gives you a range of dates instead of one.

Your body gives clues as well. The NHS says cervical mucus turns thinner and stretchy, a bit like raw egg white, around ovulation. A date from a table is a starting point, and those signs tell you more about this particular month.

A counted date isn’t birth control. The NHS says it’s possible to get pregnant soon after your period finishes if you ovulate early or have a short cycle. If you’re trying for a baby, the guide to tracking your cycle when trying to conceive covers what to log. The cycle day by day guide shows what tends to happen on the days around ovulation.

How Plum works out your ovulation day

We make Plum, a period tracker app for iPhone, so this part is about our own app. Log the day your period starts and Plum predicts your next period from your recent cycles. It counts ovulation back from that prediction, like the tables above, but uses 12 days for a cycle under 25 days and 15 for one over 32. Then it shows your fertile window. Both are free.

The estimate gets closer to your own cycle with every period you log. If you use a hormonal method like the pill, Plum hides ovulation and the fertile window by default and tells you why. Some of those methods stop ovulation altogether. Plum shows no ads and never sells personal data.